The present invention generally relates to wireless communication networks, and particularly relates to adaptive rate control of communication channels in such networks.
Evolving wireless communication networks, such as those based on the IS-2000 family of standards, offer a wide range of services including voice, data (web, email, etc.), and streaming media services. Differing applications and Quality of Service (QoS) requirements result in individual data users having differing data rate needs. IS-2000 networks typically serve individual data users on the forward link using forward link fundamental channels (F-FCHs) that support a maximum channel data rate of 9.6 kpbs. If that data rate is insufficient to meet the service requirements of a particular data user, the network assigns a forward supplemental channel (F-SCH) in conjunction with that user's F-FCH. F-SCHs are configured to have data rates expressed as a multiple of the F-FCH data rate, and thus a data user may be assigned a F-SCH rate of 1×, 2×, 4×, etc., depending on the particular service needs of that user.
Typically, the assignment of a F-SCH to a particular data user is triggered by an excess data buffer size, i.e., the queue for incoming data to be transmitted to the user is too large, or is triggered by the rate of the incoming data. Selection of a F-SCH initial data rate may be based on the predicted data throughput to the data user, or may be based on other considerations. Regardless, once the F-SCH is assigned, conventional networks either leave the initially configured rate unchanged for the duration of the assignment, or make relatively infrequent rate changes based on, for example, changes in the incoming forward link traffic (i.e., packet size or rate). In theory, the network could use frame error rate (FER) information fed back from the data user to make rate adjustments, but that would not allow timely rate adjustments because relatively long periods of time, e.g., a hundred or more received frames, are required to develop statistically accurate FER information.
Overall network performance and utilization efficiency suffer because of the inability to intelligently adjust F-SCH data rates and corresponding channel resource allocations. That is, where the data rate of a given F-SCH is too high given the current radio conditions of the data user the channel is assigned to, the effective data rate of the channel is lowered because of the high incidence of reception errors and the transmit power allocated for the inappropriately high data rate is at least partially wasted. Of course, the converse is true, wherein the network misses opportunities to make timely increases in F-SCH data rates responsive to improving radio conditions for particular data users.
Further, communication resources typically are assigned to support a targeted data rate for a given communication channel. If the actual usage of the channel is below the potential throughput possible with the assigned resources, at least a portion of those assigned resources are, in effect, being “wasted.” Thus, the utilization efficiency of the network can suffer significantly if communication channel resource allocations are not managed with respect to the actual needs of the channel users.
These circumstances are not limited to IS-2000 networks. Indeed, the potential for such inefficiencies arise in any communication network wherein rate-adjustable channels are assigned to users and managed without benefit of direct rate control feedback from the users.